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Ron Z.
Ron Z., - Buick Tech -
Category: Buick
Satisfied Customers: 17946
Experience:  18+yrs experience. State Inspector and Buick Diagnostics
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My 1995 riviera started missing. ran a check on it and the

Customer Question

my 1995 riviera started missing. ran a check on it and the machine said missing but no bank location. could it be the o2 sensor? sometimes when pushing on the gas peddle it rattles and is getting lower gas mileage
Submitted: 1 year ago.
Category: Buick
Expert:  Ron Z. replied 1 year ago.

Can you tell me what the actual p-code here was? Was it for "Random Cylinder Misfire"?

Customer: replied 1 year ago.
PO300
Expert:  Ron Z. replied 1 year ago.

Great, thanks!

Ok, the P0300 is "Random Cylinder Misfire". So, one or more of the cylinders are misfiring. Very commonly this can be the case of faulty or worn spark plugs, so this is the best place to start. Inspect the plugs for any cracks in the body or worn diodes. If there are any doubts, replace the spark plugs (and wires at the same time is a good idea). While replacing the spark plugs, it's a good idea to make sure each of the coils are firing correctly and sending spark to the plugs. If you fin d a coil that is not firing, swap it with another coil. If it still does not fire, replace the coil. If the coil does spark in the new location, then the root of the problem is the ignition control module. If the plugs look ok, and all coils are sparking, then the fuel injectors will need to be checked, an intake air leak test done and ultimately, a cylinder compression test. If my answer has helped you, please help me by leaving a rating using the stars at the top of this page or accept the answer so I may be credited. If you cannot rate or do not see the rating stars, please let me know. You can ask follow-up questions after you rate.